Unable to install WebExtension with Selenium - selenium

Question

I'm trying to test my firefox webextension but firefox refuses to install it because it doesn't have the install.rdf file. But that file is not used anymore by webextensions.
const firefox = require('selenium-webdriver/firefox');
const webdriver = require('selenium-webdriver');
require('geckodriver');
let profile = new firefox.Profile();
profile.addExtension(process.cwd() + '/build/firefox/');
profile.setPreference('extensions.firebug.showChromeErrors', true);
let options = new firefox.Options().setProfile(profile);
let _driver = new webdriver.Builder()
.forBrowser('firefox')
.setFirefoxOptions(options)
.build();
Error: ENOENT: no such file or directory, open '/dev/webext/build/firefox/install.rdf'
Is there a setting that I need to enable to tell it it's a webextension?

Answer 1

The WebExtension API is not yet supported by Selenium v3.4.0 . The method Profile::addExtension only works for a legacy addon where install.rdf is present at the root.
To test a web extension, you can either use a profile where the extension is already installed, or you can implement the custom command available with GeckoDriver since v0.17.0:
var webdriver = require('selenium-webdriver');
var Command = require('selenium-webdriver/lib/command').Command;
function installWebExt(driver, extension) {
let cmd = new Command('moz-install-web-ext')
.setParameter('path', path.resolve(extension))
.setParameter('temporary', true);
driver.getExecutor()
.defineCommand(cmd.getName(), 'POST', '/session/:sessionId/moz/addon/install');
return driver.schedule(cmd, 'installWebExt(' + extension + ')');
}
var driver = new webdriver.Builder()
.forBrowser('firefox')
.build();
installWebExt(driver, "C:\\temp\\extension.zip");

Answer 2

This is an issue with FirefoxDriver. This issue is already logged in both SeleniumHQ/selenium#4184 and
mozilla/geckodriver#759
GeckoDriver says that
A workaround for the time being would be to use the add-on endpoints
geckodriver 0.17.0 provides to get an extension installed from the
local disk.
https://github.com/mozilla/geckodriver/blob/release/src/marionette.rs#L66
So you have to use the geckodriver endpoints to do that. I have already mentioned on how to use the endpoints here